Geothermal Energy Dr. Mazen Abualtayef Environmental Engineering Department Islamic University of Gaza, Palestine
Adapted from a presentation by Professor S.R. Lawrence Leeds School of Business, Environmental Studies University of Colorado, Boulder, CO, USA
AGENDA Geothermal Energy Geothermal Overview Extracting Geothermal Energy Environmental Implications Economic Considerations Geothermal Installations Examples
Geothermal Overview
Geothermal in Context Geo = earth, thermos = heat Geothermal energy is the extractable portion of the heat stored in the ground.
Geothermal in Context World energy consumption http://en.wikipedia.org/wiki/world_energy_consumption
Geothermal in Context Global geothermal electric capacity http://en.wikipedia.org/wiki/geothermal_power
Advantages of Geothermal http://www.earthsci.org/mineral/energy/geother/geother.htm
Heat from the Earth s Center Earth's core maintains temperatures in excess of 5000 C Heat originates from radioactive decay of elements Heat energy continuously flows from hot core تدفق الحرارة بالتوصيل Conductive heat flow Convective انتقال حراري flows of molten mantle beneath the crust Mean heat flux at earth's surface 16 kilowatts of heat energy per square kilometer Dissipates to the atmosphere and space Tends to be strongest along tectonic plate boundaries Volcanic activity transports hot material to near the surface Only a small fraction of molten rock actually reaches surface Most is left at depths of 5-20 km beneath the surface Hydrological convection forms high temperature geothermal systems at shallow depths of 500-3000m. http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Earth Dynamics http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Earth Temperature Gradient http://www.geothermal.ch/eng/vision.html
Geothermal Site Schematic نبع ماء حار Boyle, Renewable Energy, 2 nd edition, 2004
Geysers Clepsydra Geyser in Yellowstone 500 geysers in yellow stone park out 1000 geysers worldwide http://en.wikipedia.org/wiki/geyser
Hot Springs Hot springs in Steamboat Springs area http://www.eia.doe.gov/cneaf/solar.renewables/page/geothermal/geothermal.html
Fumaroles Clay Diablo Fumarole (CA) White Island Fumarole New Zealand http://lvo.wr.usgs.gov/cdf_main.htm http://volcano.und.edu/vwdocs/volc_images/img_white_island_fumerole.html
Global Geothermal Sites http://www.deutsches-museum.de/ausstell/dauer/umwelt/img/geothe.jpg
Tectonic Plate Movements Enthalpy: Catchment Boyle, Renewable Energy, 2 nd edition, 2004
Extracting Geothermal Energy
Methods of Heat Extraction من تشكيل الصخور المحيطة حركة المياه من خالل محاكاة الصخور المتصدعة من المياه الجوفية الحرارية http://www.geothermal.ch/eng/vision.html
Units of Measure Pressure 1 Pascal (Pa) = 1 Newton / square meter 100 kpa = ~ 1 atmosphere 1 MPa = ~10 atmospheres Temperature Celsius (ºC); Fahrenheit (ºF); Kelvin (K) 0 ºC = 32 ºF = 273 K 100 ºC = 212 ºF = 373 K
Plants Types: 1. Dry Steam Power Plants Dry steam extracted from natural reservoir 180-225 ºC 4-8 Mpa 200+ km/hr Steam is used to drive a turbo-generator Steam is condensed and pumped back into the ground Can achieve 1 kwh per 6.5 kg of steam A 55 MW plant requires 100 kg/s of steam Boyle, Renewable Energy, 2 nd edition, 2004
Dry Steam Schematic Boyle, Renewable Energy, 2 nd edition, 2004
2. Single Flash Steam Power Plants Steam with water extracted from ground Pressure of mixture drops at surface and more water flashes to steam Steam separated from water Steam drives a turbine Turbine drives an electric generator Generate between 5 and 100 MW Use 6 to 9 tonnes of steam per hour to produce each MW of electrical power
Single Flash Steam Schematic The steam is condensed, creating a partial vacuum and thereby maximizing the power generated by the turbinegenerator. The steam is usually condensed either in a direct contact condenser, or a heat exchanger type condenser. In a direct contact condenser the cooling water from the cooling tower is sprayed onto and mixes with the steam. As an alternative to direct contact condensers shell and tube type condensers are sometimes used. Boyle, Renewable Energy, 2 nd edition, 2004
3. Binary Cycle Power Plants Low temps 100 o and 150 o C Use heat to vaporize organic liquid E.g., iso-butane, iso-pentane Use vapor to drive turbine Causes vapor to condense Recycle continuously Typically 7~12% efficient 0.1 40 MW units common http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp
Binary Cycle Schematic >2000m Boyle, Renewable Energy, 2 nd edition, 2004
Binary Plant Power Output http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
4. Double Flash Power Plants Similar to single flash operation Unflashed liquid flows to low-pressure tank flashes to steam Steam drives a second-stage turbine Also uses exhaust from first turbine Increases output 20-25% for 5% increase in plant costs
Double Flash Schematic Boyle, Renewable Energy, 2 nd edition, 2004
5. Combined Cycle Plants Combination of conventional steam turbine technology and binary cycle technology Steam drives primary turbine Remaining heat used to create organic vapor Organic vapor drives a second turbine Plant sizes ranging between 10 to 100+ MW Significantly greater efficiencies Higher overall utilization Extract more power (heat) from geothermal resource http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
6. Hot Dry Rock Technology Wells drilled 3-6 km into crust Hot crystalline rock formations Water pumped into formations Water flows through natural fissures picking up heat شقوق Hot water/steam returns to surface Steam used to generate power http://www.ees4.lanl.gov/hdr/
Hot Dry Rock Technology http://www.ees4.lanl.gov/hdr/ Fenton Hill plant
Soultz Hot Fractured Rock Boyle, Renewable Energy, 2 nd edition, 2004
2-Well HDR System Parameters 2 10 6 m 2 = 2 km 2 2 10 8 m 3 = 0.2 km 3 Boyle, Renewable Energy, 2 nd edition, 2004 معاوقة لتيار كهربائي Impedance:
Promise of HDR 1 km 3 of hot rock has the energy content of 70,000 tons of coal If cooled by 1 ºC Upper 10 km of crust in US has 600,000 times annual US energy (USGS) Between 19-138 GW power available at existing hydrothermal sites Using enhanced technology Boyle, Renewable Energy, 2 nd edition, 2004
Direct Use Technologies Geothermal heat is used directly rather than for power generation Extract heat from low temperature geothermal resources < 150 o C Applications sited near source (<10 km) Using heat pump technology to utilize geothermal heat for air conditioning and refrigeration applications http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Geothermal Heat Pump http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp
Vertical Geothermal Loop Ramallah example Video Installation Video
Heat vs. Depth Profile Boyle, Renewable Energy, 2 nd edition, 2004
Geothermal District Heating Southhampton geothermal district heating system technology schematic Boyle, Renewable Energy, 2 nd edition, 2004
Direct Heating Example Boyle, Renewable Energy, 2 nd edition, 2004
Technological Issues Geothermal fluids can be corrosive Contain gases such as hydrogen sulphide Corrosion Requires careful selection of materials and diligent operating procedures Typical capacity factors of 85-95% http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Technology vs. Temperature Reservoir Temperature High Temperature >220 o C Intermediate Temperature 100-220 o C Low Temperature 50-150 o C Reservoir Fluid Water or Steam Water Water Common Use Power Generation Direct Use Technology commonly chosen Flash Steam Combined (Flash and Binary) Cycle Direct Fluid Use Heat Exchangers Heat Pumps Power Generation Direct Use Binary Cycle Direct Fluid Use Heat Exchangers Heat Pumps Direct Use Direct Fluid Use Heat Exchangers http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Geothermal Performance Boyle, Renewable Energy, 2 nd edition, 2004
Current Geothermal Projects
Environmental Implications
Environmental Impacts Land Air Vegetation loss Soil erosion Landslides Slight air heating Local fogging Ground Reservoir cooling Seismicity (tremors) الزلزالية )الهزات ) Water using water for drilling purpose: Watershed impact Divert streams using water from reservoir: Lower water table هبوط Subsidence Noise -- Disturbance to animals & humans Benign overall بشكل عام غير خطر http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Renewable? Heat depleted as ground cools Not steady-state Earth s core does not replenish/refill heat to crust quickly enough Example: -- The government of Iceland states It should be stressed that the geothermal resource is not strictly renewable in the same sense as the hydro resource. It estimates that Iceland's geothermal energy could provide 1700 MW for over 100 years, compared to the current production of 140 MW. http://en.wikipedia.org/wiki/geothermal
Geothermal Calculator A geothermal calculator was developed by Mazen Abualtayef and you can find it here http://site.iugaza.edu.ps/mab ualtayef/files/pvcalculator.xlsx
Economics of Geothermal
Cost Factors Temperature and depth of resource: A shallow resource means minimum drilling costs. High temperatures mean higher energy capacity Type of resource (steam, liquid, mix): A dry steam resource is generally less expensive to develop as reinjection pipelines, separators and reinjection wells are not required Chemistry of resource: A resource with high salinity fluids, high silica concentrations, high gas content, or acidic fluids can pose technical problems which may be costly to overcome Permeability of rock formations: A highly permeable resource means higher well productivity Size and technology of plant Infrastructure (roads, transmission lines) http://www.worldbank.org/html/fpd/energy/geothermal/cost_factor.htm
Costs of Geothermal Energy Costs highly variable by site Dependent on many cost factors High exploration costs High initial capital, low operating costs Fuel is free Significant exploration & operating risk Adds to overall capital costs http://www.worldbank.org/html/fpd/energy/geothermal/
Cost of Water & Steam High temperature (>150 o C) Medium Temperature (100-150 o C) Low Temperature (<100 o C) Cost (US $/ton of steam) 3.5-6.0 Cost (US /ton of hot water) 3.0-4.5 20-40 10-20 Table Geothermal Steam and Hot Water Supply Cost where drilling is required http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Cost of Geothermal Power Small plants (<5 MW) Medium Plants (5-30 MW) Large Plants (>30 MW) Unit Cost (US /kwh) High Quality Resource Unit Cost (US /kwh) Medium Quality Resource Unit Cost (US /kwh) Low Quality Resource 5.0-7.0 5.5-8.5 6.0-10.5 4.0-6.0 4.5-7 Normally not suitable 2.5-5.0 4.0-6.0 Normally not suitable http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Direct Capital Costs Plant Size High Quality Resource Medium Quality Resource Low Quality Resource Small plants (<5 MW) Exploration : US$400-800 Steam field:us$100-200 Power Plant:US$1100-1300 Total: US$1600-2300 Exploration : US$400-1000 Steam field:us$300-600 Power Plant:US$1100-1400 Total: US$1800-3000 Exploration : US$400-1000 Steam field:us$500-900 Power Plant:US$1100-1800 Total:US$2000-3700 Med Plants (5-30 MW) Exploration : US$250-400 Steamfield:US$200-US$500 Power Plant: US$850-1200 Total: US$1300-2100 Exploration: : US$250-600 Steam field:us$400-700 Power Plant:US$950-1200 Total: US$1600-2500 Normally not suitable Large Plants (>30 MW) Exploration:: US$100-200 Steam field:us$300-450 Power Plant:US$750-1100 Total: US$1150-1750 Exploration : US$100-400 Steam field:us$400-700 Power Plant:US$850-1100 Total: US$1350-2200 Normally not suitable Direct Capital Costs (US $/kw installed capacity) http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Indirect Costs Availability of skilled labor Infrastructure and access Political stability Indirect Costs Good: 5-10% of direct costs in developed countries Fair: 10-30% of direct costs Poor: 30-60% of direct costs in developing countries http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Operating/Maintenance Costs O&M Cost (US c/kwh) Small plants (<5 MW) O&M Cost (US c/kwh) Medium Plants (5-30 MW) O&M Cost (US c/kwh) Large Plants(>30 MW) Steam field 0.35-0.7 0.25-0.35 0.15-0.25 Power Plant 0.45-0.7 0.35-0.45 0.25-0.45 Total 0.8-1.4 0.6-0.8 0.4-0.7 http://www.worldbank.org/html/fpd/energy/geothermal/assessment.htm
Geothermal Installations Examples
Geothermal Power Examples Boyle, Renewable Energy, 2 nd edition, 2004
Geothermal Power Generation World production of 8 GW 2.7 GW in US The Geysers (US) is world s largest site Produces 2 GW Other attractive sites Rift region منطقة الصدع of Kenya, Iceland, Italy, France, New Zealand, Mexico, Nicaragua, Russia, Phillippines, Indonesia, Japan http://en.wikipedia.org/wiki/geothermal
Geothermal Energy Plant http://www.wateryear2003.org/en/ Geothermal energy plant in Iceland
Geothermal Well Testing Geothermal well testing, Zunil, Guatemala http://www.geothermex.com/es_resen.html
Heber Geothermal Power Station 52kW electrical generating capacity http://www.ece.umr.edu/links/power/geotherm1.htm
Geysers Geothermal Plant The Geysers is the largest producer of geothermal power in the world. http://www.ece.umr.edu/links/power/geotherm1.htm
Geyers Cost Effectiveness Boyle, Renewable Energy, 2 nd edition, 2004
Geothermal Summary
Geothermal Prospects Environmentally very attractive Attractive energy source in right locations Likely to remain an adjunct مساعد to other larger energy sources Part of a portfolio of energy technologies Exploration risks and up-front capital costs remain a barrier
Next Week: BIOENERGY
Supplementary Slides Extras
Geothermal Gradient http://www.earthsci.org/mineral/energy/geother/geother.htm
Geo/Hydrothermal Systems http://www.freeenergynews.com/directory/geothermal/
Location of Resources http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp
Ground Structures Boyle, Renewable Energy, 2 nd edition, 2004
Volcanic Geothermal System Boyle, Renewable Energy, 2 nd edition, 2004
Temperature Gradients Boyle, Renewable Energy, 2 nd edition, 2004
http://www.earthsci.org/mineral/energy/geother/geother.htm
UK Geothermal Resources Boyle, Renewable Energy, 2 nd edition, 2004
Porosity vs. Hydraulic Conductivity Boyle, Renewable Energy, 2 nd edition, 2004
Performance vs. Rock Type Boyle, Renewable Energy, 2 nd edition, 2004
Deep Well Characteristics Boyle, Renewable Energy, 2 nd edition, 2004
Single Flash Plant Schematic http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
http://www.worldbank.org/html/fpd/energy/geothermal/technology.htm
Binary Cycle Power Plant http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp
Flash Steam Power Plant http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp
Efficiency of Heat Pumps Boyle, Renewable Energy, 2 nd edition, 2004
Recent Developments Comparing statistical data for end-1996 (SER 1998) and the present Survey, it can be seen that there has been an increase in world geothermal power plant capacity (+9%) and utilisation (+23%) while direct heat systems show a 56% additional capacity, coupled with a somewhat lower rate of increase in their use (+32%). Geothermal power generation growth is continuing, but at a lower pace than in the previous decade, while direct heat uses show a strong increase compared to the past. Going into some detail, the six countries with the largest electric power capacity are: USA with 2 228 MWe is first, followed by Philippines (1 863 MWe); four countries (Mexico, Italy, Indonesia, Japan) had capacity (at end-1999) in the range of 550-750 MWe each. These six countries represent 86% of the world capacity and about the same percentage of the world output, amounting to around 45 000 GWhe. The strong decline in the USA in recent years, due to overexploitation of the giant Geysers steam field, has been partly compensated by important additions to capacity in several countries: Indonesia, Philippines, Italy, New Zealand, Iceland, Mexico, Costa Rica, El Salvador. Newcomers in the electric power sector are Ethiopia (1998), Guatemala (1998) and Austria (2001). In total, 22 nations are generating geothermal electricity, in amounts sufficient to supply 15 million houses. Concerning direct heat uses, Table 12.1 shows that the three countries with the largest amount of installed power: USA (5 366 MWt), China (2 814 MWt) and Iceland (1 469 MWt) cover 58% of the world capacity, which has reached 16 649 MWt, enough to provide heat for over 3 million houses. Out of about 60 countries with direct heat plants, beside the three abovementioned nations, Turkey, several European countries, Canada, Japan and New Zealand have sizeable capacity. With regard to direct use applications, a large increase in the number of GHP installations for space heating (presently estimated to exceed 500 000) has put this category in first place in terms of global capacity and third in terms of output. Other geothermal space heating systems are second in capacity but first in output. Third in capacity (but second in output) are spa uses followed by greenhouse heating. Other applications include fish farm heating and industrial process heat. The outstanding rise in world direct use capacity since 1996 is due to the more than two-fold increase in North America and a 45% addition in Asia. Europe also has substantial direct uses but has remained fairly stable: reductions in some countries being compensated by progress in others. Concerning R&D, the HDR project at Soultz-sous-Forêts near the French-German border has progressed significantly. Besides the ongoing Hijiori site in Japan, another HDR test has just started in Switzerland (Otterbach near Basel). The total world use of geothermal power is giving a contribution both to energy saving (around 26 million tons of oil per year) and to CO2 emission reduction (80 million tons/year if compared with equivalent oil-fuelled production). http://www.worldenergy.org/wec-geis/publications/reports/ser/geo/geo.asp